VOLCANISM ASSOCIATED WITH CRUSTAL EXTENSION IN THE BASIN AND RANGE PROVINCE

The state of Nevada lies within the Basin and Range Province, an area characterized by alternating, north-south trending, faulted mountains and flat valley floors. This region has formed in response to crustal extension which has led to the production and emplacement of numerous basalts and rhyolites across the area. The aim of this study is to characterize and evaluate the nature of the magmatism associated with this period of crustal extension.

Specifically, basalts and rhyolites were sampled throughout the Big Smokey Valley which lies approximately 250 miles northwest of Las Vegas and to the north of the mining town of Tonopah. Investigation of these samples aims to further our understanding of not only the origin of magmas produced during extension of the Earth’s lithosphere in the western USA, but also the timing of magmatism associated with Basin and Range extension in this part of the province.

Preliminary field work was undertaken in the Spring of 2019. Thin sections of both the basalts and rhyolites form the basis of our initial study. Future work will entail detailed petrographic and mineralogical characterization via Scanning Electron Microscopy (SEM) equipped with EDS, in addition to bulk geochemical analyses (major and trace elements) and in-situ chemical analyses of major and minor phases.

Our preliminary observations highlight the dominantly porphyritic, felsic nature of sampled rhyolites with significant amounts of Quartz and Potassium Feldspar with accessory apatite and zircon. Sampled basaltic samples lack vesicularity and are dominated by Olivine, Plagioclase Feldspar, and Clinopyroxene.

It is anticipated that collectively the study of this compositionally bimodal suite will advance our understanding of Basin and Range related magmatism in addition to providing insights into the generation of magmas during lithospheric extension.